Patent application title: INDEXABLE INSERT FOR MILLING TOOLS

Abstract:

The invention relates to an indexable insert for a milling tool.
Furthermore, the invention relates to a milling tool, in particular for
machining crankshafts or camshafts. In order to create a milling tool, in
particular for machining crankshafts and camshafts, which runs smoothly
with reduced drive power consumption at a high cutting capacity, it is
provided according to the invention that the indexable insert (1) used
has at least on one side a centrically symmetrical cutting edge contour
(4, 4'), wherein in plan view the cutting face (2, 2') has a concave
wedge shape or trough shape with an angle α of the wedge base or
trough base (21) to the mounting surface (3, 3') and on the opening side
of the angle α the cutting edge (4, 4') formed by the mounting
surface or lateral surface (3, 3') and the cutting face (2, 2') is
rounded.

Claims:

1. Indexable insert (1) for a milling tool, in particular for machining
crankshafts or camshafts with at least one mounting surface (3) having a
through bore (5) for fixing to a rotatable tool and at least one cutting
face (2, 2') forming cutting edges (4) with the lateral surfaces,
characterized in that the indexable insert (1) has a centrically
symmetrical cutting edge contour (4, 4') on at least one side, wherein
the cutting face (2, 2') has a concave wedge shape or trough shape with
an angle α of the wedge base or trough base (21) to the mounting
surface (3, 3') and in plan view of the cutting face (2, 2') on the
opening side of the angle α the cutting edge (4, 4') formed by the
mounting surface or the lateral surface (3, 3') and the cutting face (2,
2') is rounded.

2. Indexable insert (1) according to claim 1, characterized in that the
wedge angle δ (kappa) of the cutting edge (4, 4'), measured
perpendicular to the wedge base or trough base (21, 21'), is 50.degree.
to 85.degree..

3. Indexable insert (1) according to claim 1, characterized in that the
insert (1) has cutting faces (2, 2', 2'', 2''') identically spaced apart
and identically shaped on both sides, based on the through bore (5).

4. Indexable insert (1) according to claim 1, characterized in that the
cutting face (2, 2') has perpendicular on the wedge base or trough base
(21) a flat wedge shape or a trough shape with a straight-line generatrix
and is produced by machining, e.g., by grinding.

5. Milling tool, in particular for machining crankshafts or camshafts,
characterized in that indexable inserts according to one of the preceding
claims are arranged on at least one side of an essentially disk-shaped
tool body such that their cutting angle has a value of zero or greater
than zero.

6. Milling tool according to claim 5, characterized in that the cutting
angle is no more than 20.degree., preferably no more than 15.degree..

Description:

[0001]The invention relates to an indexable insert for a milling tool.

[0002]To be more precise, the invention relates to an indexable insert for
a milling tool for machining crankshafts or camshafts with at least one
mounting surface having a bore for fixing to a rotatable tool part and at
least one cutting face forming cutting edges with the lateral surfaces.

[0003]Furthermore, the invention relates to a milling tool, in particular
for machining crankshafts or camshafts.

[0004]Inserts for milling tools, in particular for machining crankshafts,
generally have a wedge angle, that is the angle on the cutting edge from
the side face to the cutting face of the insert, of 90°. When
installed in the milling tool, this means that the cutting angle of the
insert is negative and has a value of approx. -8° to -12°.
One skilled in the art refers to this as "negative (insert) geometry."

[0005]In the practical use of the milling tool, a wedge angle of
90° produces a high edge-holding ability of the insert, however,
the negative geometry causes strong cutting forces during cutting.

[0006]However, strong cutting forces on the milling tool highly load the
transmission drive of the milling cutter, wherein this must be free from
play and may not permit any chatter vibrations at all.

[0007]A reduction of the cutting forces on an insert and thus a reduction
in the load on the milling cutter drive can be achieved, as one skilled
in the art is aware, through a so-called positive geometry of the cutting
edge. With a cutting angle of less than 90°, a wedge angle of the
insert on the cutting edge of 82° to 70° should be
provided.

[0008]Attempts have already been made to use indexable inserts with a
cutting cavity recessed from the cutting edge on all sides and in this
manner to create a positive geometry of the cutting edge of the milling
tool. Although this geometry of the cutting edge of the insert can
largely meet the expectations with respect to a reduction of the cutting
forces and thus cause a reduction of the load on the tool drive working
free from play, it has the disadvantages of a complex production, a low
cutting edge-holding ability and an insert geometry associated with high
dimensional tolerances and uneven or unmachined sintered bearing
surfaces.

[0009]The object of the invention is now to create an indexable insert for
a milling tool of the type mentioned at the outset, which causes a high
chip removal with reduced cutting forces in the tool, in particular with
a machining of crankshafts, has a largely positive geometry of the
cutting edge, reduces the cutting pressure on the cutting faces in the
area of the cutting edge, has a high manufacturing accuracy and ensures
high cost effectiveness and insert quality in terms of manufacturing
technology.

[0010]Furthermore, the object of the invention is to disclose a milling
tool which runs smoothly with reduced drive power consumption at a high
cutting capacity.

[0011]The former object is attained with a generic indexable insert in
that it has a centrically symmetrical cutting edge contour on at least
one side, wherein in plan view the cutting face has a concave wedge shape
or trough shape with an angle α of the wedge base or trough base to
the mounting surface and on the opening side of the angle α the
cutting edge formed by the mounting surface or the lateral surface and
the cutting face is rounded.

[0012]The advantages attained with the invention are essentially that the
cutting edge contour is adjusted to the criteria of a high chip removal
during milling and for an indexing of the insert. The cutting face is
thereby embodied such that on the one hand it realizes a desired geometry
of the cutting edge and cutting edge embodiment, and on the other hand
can guarantee a secure non-displaceable support of the insert. In order
to create a cutting contour shape that is favorable for milling,
curvatures are provided on two corners lying opposite one another,
wherein a wedge angle that is necessary for a positive geometry in the
round areas of the insert is obtained through an angular position of the
concave cutting face base to the mounting surface.

[0013]According to a preferred embodiment of an insert according to the
invention, the wedge angle κ (kappa) of the cutting edge, measured
perpendicular to the wedge base or trough base, is 50° to
85°.

[0014]A wedge angle of this type permits an advantageous positioning of
the insert in the milling cutter and provides a high cutting edge-holding
ability or a low risk of cutting edge chips in the highly stressed zones.

[0015]If, as can be advantageously provided, the insert has cutting faces
identically spaced apart and identically shaped on both sides, based on
the through bore, an indexing with a provision of a total of four new
cutting areas is possible.

[0016]An embodiment of an indexable insert according to the invention that
is favorable in terms of production technology and excellent in
particular for chip formation can be obtained in that the cutting face
has perpendicular on the wedge or trough base a flat wedge shape or a
trough shape with a straight-line generatrix and is produced by
machining, e.g., by grinding.

[0017]A chip flowing off from the cutting edge on the cutting face is
subjected thereby to only a low pressure against the travel direction
caused by a bending, so that a wear and the thermal load are minimized.
Furthermore, the dimensional variations of the inserts are kept small and
smooth cutting faces are created for the flow of chips in a favorable
manner through a machining.

[0018]The further object of the invention is attained with a milling tool
in that indexable inserts according to the above descriptions are
arranged on at least one side of an essentially disk-shaped tool body
such that their cutting angle has a value of zero or greater than zero.

[0019]The advantages attained with a milling tool according to the
invention are essentially that the indexable insert is installed in a
simple manner such that a positive geometry of the cutting edge is given
in the areas where the greatest chip removal takes place, which has its
advantages in particular in an efficient cutting with low cutting
pressure and chatter-free drive with reduced power.

[0020]Advantageously, the milling tool is embodied in an embodiment of the
invention such that the cutting angle is no more than 20°,
preferably no more than 15°.

[0021]In this manner fractures of the cutting edge can be effectively
avoided.

[0022]The invention is described in more detail below based on drawings
showing only one execution method.

[0023]They show:

[0024]FIG. 1 an insert;

[0025]FIG. 2 an insert in a view parallel to the mounting surface;

[0026]FIG. 3 an insert in a view parallel to the bore axis;

[0027]FIG. 4 an insert in plan view of the cutting faces;

[0028]FIG. 5 an insert in a view parallel to the cutting faces;

[0029]FIG. 6 a milling tool in section with separated insert.

[0030]FIG. 1 shows an insert 1 with a mounting surface 3 on a tool and
with a through bore 5 for attaching the same thereto. A tangential
indexable insert 1 according to an embodiment of the invention has on the
front a flat cutting face 2 and a like cutting face 2', which form with
one another a concave end-face wedge shape with a wedge base 21. The
cutting faces 2, 2' and the mounting surfaces 3, 3' of the insert form
cutting edges 4, 4', 4'', which have a curvature diagonally opposite,
wherein the wedge base 21 runs in a diagonally opposite manner and in
this manner enlarged cutting faces 2, 2' are formed in the curvature
region.

[0031]FIG. 2 shows in a view an insert according to FIG. 1 parallel to the
mounting surfaces 3, 3' or lateral surfaces. A wedge base 21 runs
obliquely at an angle to the lateral surfaces 3, 3', wherein cutting
edges 4, 4' are formed with the cutting faces.

[0032]FIG. 3 shows an insert according to FIG. 2, but in a view rotated by
90° in the direction of the bore 5.

[0033]FIG. 4 shows schematically an insert 1 according to the invention in
a plan view, parallel to the mounting surfaces, of the cutting faces 2,
2', which form a wedge base 21.

[0034]FIG. 5 shows the insert 1 in the view from A in the direction of the
wedge base 21.

[0035]The wedge base 21 runs at an angle α to the flat mounting
surface 3' and provides an optionally flat cutting face 2', which is
enlarged towards the curvature of the lateral surface. The cutting faces
2, 2' and the cutting edges 4, 4' are thereby embodied in a centrically
symmetrical manner. In the plan view of the cutting faces 2, 2', with a
length of approx. 16 mm and a width of approx. 6.5 mm of the indexable
insert, the angle α can be, for example, approximately 12°.

[0036]FIG. 5 shows a concave wedge shape of the cutting faces 2, 2' and
equally spaced from the bore 5 that of the cutting faces 2'' and 2''',
which respectively form a wedge base 21 and 21'. The mounting surfaces or
lateral surfaces 3, 3' and the cutting faces 2, 2', 2'', 2''' form a
wedge angle κ (kappa) perpendicular to this wedge base 21, 21' on
the cutting edges 4, 4', 4'', 4'''.

[0037]According to the invention, the cutting face region can also be
embodied in a cylindrical or trough-shaped manner with a straight-line
generatrix, wherein a different wedge angle optionally results in the
curved area of the cutting edges 4, 4', 4'', 4'''.

[0038]FIG. 6 shows a section from a milling tool F, which perpendicular to
the radius R on a tool outer side W has a recess B for a separately shown
indexable insert 1 according to the invention. The tool movement is
labeled by 0.